A novel Non-Newtonian fluid polishing technique for zirconia ceramics based on the weak magnetorheological strengthening thickening effect

Zirconia ceramics have excellent physical and chemical properties and have several applications. However, owing to their hardness and brittleness, it is difficult to realise the non-destructive high-efficiency machining of zirconia ceramics. Herein, we propose an efficient non-Newtonian fluid polishing method for zirconia ceramics based on the weak magnetorheological strengthening thickening effect. The nanoscale material removal and evolution mechanisms of the zirconia ceramic surface were investigated. Based on the results obtained through scanning electron microscopy and a derivation of the fluid shear stress model in the polishing zone, we clarify the microscopic material removal mechanism during the machining process, and establish the prediction model of material removal rate. The detection results of the surface quality were in good agreement with the established material removal mechanism. The model of material removal rate could predict the processing effectively, and the average relative error was 4.45%. The experimental results demonstrate that the proposed weak magnetorheological shear thickening polishing (WMRSTP) method can realise lossless, self-adaptive, ultra-precision machining of a hemispherical zirconia ceramic workpiece. Compared to the traditional non-Newtonian fluid polishing method, the polishing quality and polishing efficiency of this method are significantly improved. The surface roughness Sa, the surface accuracy PV, and the material removal rate MRR of the zirconia hemispherical workpiece after 1 h of WMRSTP were 13.2 nm, 0.104 μm, and 5.96 μm/h, respectively.